The present invention is directed toward disc brakes, and more particularly toward a pad wear compensator for a disc brake caliper.
Disc brakes are being included on more and more bicycles as consumers are ever increasingly demonstrating a preference for disc brakes over conventional rim brakes such as caliper brakes, cantilever brakes and side pull cantilever brakes. While both mechanical and hydraulic disc brakes have been available for bicycles for many years, only recently have there been advances in disc brake caliper design that have made disc brakes sufficiently lightweight, reliable and inexpensive to satisfy consumer preferences. While more efficient and powerful caliper drive mechanisms are evolving, to date manufacturers of disc brakes have not adequately addressed consumer need for ease of adjustment and maintenance of these caliper brakes. One area of particular concern is structures for compensating for pad wear.
One known pad wear compensator provides a set screw that can be advanced within a caliper housing to advance an operatively associated brake pad as the pad wears. The set screw resides within a threaded bore in the housing and requires a turning tool such as a hex wrench to advance the pad. In addition, to lock the pad in a select position, a second locking screw is threadably engaged in the bore to lock the adjustment screw in place. This structure, while allowing for advancement of the pad to compensate for pad wear, is extremely cumbersome to use, requiring the removal of one screw and the turning of two screws as well as the use of a separate tool to make an adjustment. In addition, because the adjustment screw resides within the threaded bore, there is no reliable way to gauge how far the pad has been extended so as to assess remaining pad life. Furthermore, the structure fails to provide any indexing to insure select axial advancement of the brake pad as the adjustment screw is rotated.
Another known pad wear compensator provides a knob which can be rotated to advance the caliper housing relative to a disc operatively associated with the housing so as to compensate for brake pad wear. While this structure overcomes some of the complexity and tool requirements of the structure discussed in the preceding paragraph, it still has numerous deficiencies. Most notably, by providing for advancement of the entire housing relative to the disc as opposed to simply advancement of the pad itself relative to the housing and the disc as it wears, the advancement structure must reside outside of the housing and is thus subject to damage and abuse in use. In addition, while this structure does allow for observation of how far the housing has been advanced relative to the disc, it does not provide a reliable indication of pad wear, as adjustment of the housing may be dictated by other factors such as disc alignment.
Yet another known pad wear compensator provides a knob which threadably engages a caliper housing. The knob can be rotated relative to the caliper housing and thus advanced and retracted axially of the housing. As the knob is rotated to advance it relative to the housing it also advances a pad actuation mechanism along with a pad assembly associated therewith to advance the pad assembly. The opposing pad is fixed against movement relative to the housing. However, the housing itself is moveable relative to a disc so that by movement of the caliper housing and movement of the pad wear compensation knob, pad wear on each of the pads can be compensated for. This structure is still very cumbersome in that only one pad can be advanced relative to the housing. In addition, the knob both rotates and is advanced relative to the housing, providing a potential avenue for grit and other contaminates to effect smooth operation of the caliper actuation mechanism. Finally, because the housing itself is moveable relative to the disc to enable compensation of the fixed pad, there is no reliable indication of how much wear the respective pads have experienced.
German Patent Publication DE 2648765 A1 discloses yet another system to compensate for the wear of brake pads on a disc brake. This system includes a caliper housing which floats on an attachment bracket relative to a frame to which the caliper brake is attached. A pair of brake pad assemblies within the caliper housing receive a disc therebetween. A drive mechanism is operatively associated with a first one of the brake pad assemblies to advance and retract the first brake pad assembly relative to the disc along an advancement axis to effect braking. An adjustment knob is attached to the housing for rotation about a rotation axis. A rotary to linear linkage provides axial advancement of the first brake pad assembly relative to the housing upon axial rotation of the knob in a select direction. While this structure has the advantage of providing axial advancement of a brake pad assembly relative to a caliper housing, because the caliper housing floats it does not provide a structure for fixing a select distance between a brake pad and a brake disc. As a result, the structure taught in DE 2648765 A1 does not eliminate the possibility of the linked brake pad assembly contacting the disc when in the retracted position. This can be a considerable problem for use in bicycles where such contact results in friction diminishing the efficient turning of the bicycle wheels. DE 2648765 A1 further fails to teach or suggest any structure for indication of pad wear. Moreover, because DE 2648765 A1 teaches a floating caliper, there is no teaching or suggestion of any desirability of providing a structure for advancing the brake pad which is not operatively associated with the drive mechanism.
The present invention is intended to overcome one or more of the problems discussed above.
A mechanical bicycle disc brake includes a caliper housing configured to be attached to a bicycle frame fixed against lateral movement relative to the bicycle frame. A pair of brake pad assemblies are received within the housing and are configured to reside on opposite sides of the disc operatively associated therewith. At least one brake pad assembly is operatively associated with a drive mechanism configured to advance and retract the brake pad assembly relative to the disc along an advancement axis to effect braking. An adjustment knob is attached to the housing for rotation about a rotation axis but fixed against axial movement. A rotary to linear linkage is operatively associated with at least one of the brake pad assemblies and the knob to provide axial advancement of the at least one linked brake pad assembly relative to the housing and the disc upon axial rotation of the knob in a select direction to fix a select distance between the at least one linked brake pad assembly and the disc with the at least one brake pad assembly retracted. The mechanical bicycle disc brake may further include an indicator visibly observable outside the housing. The indicator is operatively associated with the rotary to liner linkage to advance with the brake pad assembly as the adjustment knob is rotated in the select direction. The rotation axis and the advancement axis may be the same and the visual indicator preferably extends into a hole in the knob along the rotation axis. A tactile indicator may be associated with the knob for providing a tactile indication of advancement of the brake pad assembly along the advancement axis a select amount as the knob is rotated in the select direction. The tactile indicator preferably includes index knurls within the housing that are fixed against rotation relative to the knob and complimentary detents operatively associated with the knob engaging the knurls as the knob is rotated relative to the detents.
Another aspect of the present invention is a mechanical bicycle disc brake including the caliper housing configured to be attached to a bicycle frame fixed against lateral movement relative to the bicycle frame. A pair of first and second brake pad assemblies are received within the housing and configured to reside on opposite sides of a disc operatively associated therewith. A drive mechanism within the housing is operatively associated with the first brake pad assembly and configured to advance and retract the first brake pad assembly relative to the disc along an advancement axis to effect braking. A first adjustment knob is attached to the housing for rotation about a first rotation axis but fixed against axial movement. A second adjustment knob is attached to the housing for rotation about a second rotation axis but fixed against axial movement. A first rotary to linear linkage between the first brake pad assembly and the first knob provide axial advancement of the first brake pad assembly relative to the housing and the disc upon axial rotation of the knob in a select direction to fix a select distance between the first brake pad assembly and the disc with the first brake pad retracted. A second rotary to linear linkage between the second brake pad assembly and the second knob provides axial advancement of the second brake pad assembly relative to the housing and the disc upon axial rotation of the knob in a select direction to fix a select distance between the second brake pad assembly and the disc with the first brake pad retracted. An indicator visibly observable outside the housing may be operatively associated with each of the first and second rotary to linear linkages to advance with the respective first and second brake pad assemblies as the first and second adjustment knobs are rotated in the select direction.
The mechanical bicycle disc brake of the present invention includes a pad wear compensation apparatus that allows for quick and easy advancement of the brake pads relative to the housing to compensate for brake pad wear. The knobs allow for this adjustment to be made without tools, allowing the adjustment to be made anywhere and at any time with minimal effort by the user. Because the knobs rotate but do not advance axially with the remainder of the pad wear compensation apparatus, the opportunity for grit or the like contaminating the apparatus is minimized. The tactile indicator of the pad wear compensation apparatus gives immediate tactile feedback to a user to indicate a select distance of pad advancement for a select increment of rotation of the knob. The pad wear compensation apparatus also includes a visual indicator giving an immediate visual indication to the user of how far the brake pad has been advanced relative to the housing. In this manner a user can continuously monitor the amount of pad wear left so as to minimize the possibility of excessive pad wear during an extended ride which could cause scoring and ultimately the ruining of an associated disc. The mechanical disc brake further allows a brake pad assembly to be fixed a select distance from the disc in a retracted position to eliminate friction causing rubbing. In one embodiment a pad wear compensation apparatus is operatively associated with each brake pad assembly so each brake pad assembly may be independently spaced a fixed select distance from the disc. All these many advantages are provided by the pad wear compensation apparatus that consists of simple mechanical elements that can be produced and assembled inexpensively and which provide highly reliable and convenient adjustment.